1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a method for fabricating an LCD having a liquid crystal dropping method applied thereto.
2. Background of the Related Art
Keeping pace with development of an information-oriented society, demands on displays increase gradually in a variety of forms and, recently, to meet the demands, different flat display panels, such as Liquid Crystal Display (LCD), Plasma Display Panel (PDP), Electro Luminescent Display (ELD), Vacuum Fluorescent Display (VFD), and the like, have been under development, some of which are employed as displays in various apparatuses.
The LCDs have been most widely used the as mobile displays, while replacing the Cathode Ray Tube (CRT), owing to features and advantages of excellent picture quality, lightweight, thin size, and low power consumption. Besides the mobile-type LCDs of the notebook computer monitors, the LCDs are under development for televisions (TVs) for receiving and displaying broadcasting signals, and computer monitors.
Despite the various technical developments in the LCD, for serving as a display in different fields, the studies for enhancing the picture quality of the LCD as a display are inconsistent with the features and advantages of the LCD in many aspects. Therefore, for employing the LCD in various fields as a general display, the key to development of the LCD lies in whether the LCD can implement a high-quality picture such as high definition, high luminance, and a large sized screen, while having a lightweight, thin size, and a low power consumption.
The LCD is provided with a liquid crystal display panel for displaying a picture and a driving part for providing a driving signal to the liquid crystal display panel, wherein the liquid crystal display panel has first and second glass substrates bonded together with a gap between the substrates, and a liquid crystal layer injected between the first and second glass substrates.
On the first glass substrate, a thin film transistor (TFT) array substrate, there are a plurality of gatelines arranged in one direction at fixed intervals, a plurality of datalines arranged in a direction perpendicular to the gatelines at fixed intervals, a plurality of pixel electrodes in respective pixel regions defined at crossing points of the gatelines and the datalines to form a matrix, a plurality of thin film transistors switchable in response to a signal from the gatelines for transmission of a signal from the dataline to the pixel electrodes.
The second glass substrate (a color filter substrate) has a black matrix layer for shielding light from parts excluding the pixel regions, a red, green, blue (RGB) color filter layer for displaying colors, and a common electrode for implementing a picture.
The foregoing first and second substrates are bonded together, spaced by spacers, with sealant having a liquid crystal injection opening therein, through which liquid crystal is injected.
The liquid crystal is injected by evacuating the space between the bonded two substrates and dipping the liquid crystal injection opening in liquid crystal. The liquid crystal flows in the space between the two substrates by the capillary tube phenomenon. Once the liquid crystal is injected, the liquid crystal injection opening is sealed by the seal.
However, the related art method for fabricating an LCD having the liquid crystal injection method applied thereto has the following problems.
First, the related art method has a poor productivity because the dipping of the liquid crystal injection opening in a liquid crystal while the space between the two substrates are maintained at a vacuum for injection of the liquid crystal takes a long time.
Second, liquid crystal injection, particularly into a large-sized LCD, is likely to cause imperfect filling of the liquid crystal in the panel, which is a cause of a defective panel.
Third, the complicated and lengthy fabrication process results in a requirement for many liquid crystal injection devices, which occupy much space.
Accordingly, a method for fabricating an LCD by using a liquid crystal dropping method has been under research recently. A Japanese laid-open patent publication No. 2000-147528 discloses the following liquid crystal dropping method.
A related art method for fabricating an LCD having the foregoing liquid crystal dropping method applied thereto will be explained. FIGS. 1A-1F the steps of a related art method for fabricating an LCD.
Referring to FIG. 1A, UV sealant 1 is coated on a first glass substrate 3 having a thin film transistor array formed thereon to a thickness of approximately 30 xcexcm and liquid crystal 2 is dropped on an inner side of seal 1 (a thin film transistor array part). No liquid crystal injection opening is provided in seal 1.
The first glass substrate 3 is mounted on a table 4 in a vacuum container xe2x80x98Cxe2x80x99 which is movable in a horizontal direction and held by a first suction device 5 holding an entire bottom surface of the first glass substrate 3 by vacuum.
Referring to FIG. 1B, an entire bottom surface of the second glass substrate 6 having the color filter array formed thereon is held by a second suction device 7 by vacuum and the vacuum container xe2x80x98Cxe2x80x99 is closed and evacuated. The second suction device 7 is moved down in a vertical direction until a gap between the first and second glass substrate 3 and 6 becomes approximately 1 mm and the table 4 with the first glass substrate 3 thereon is moved in a horizontal direction, to pre-align the first and second glass substrates 3 and 6.
Referring to FIG. 1C, the second suction device 7 is moved down until the second glass substrate 6 comes into contact with the liquid crystal 2 or the seal 1.
Referring to FIG. 1D, the table 4 with the first glass substrate 3 thereon is moved in a horizontal direction to align the first and second glass substrates 3 and 6.
Referring to FIG. 1E, the second suction device 7 is moved down until the second glass substrate 6 comes into contact with the seal 1 and is pressed down until a gap between the second glass substrate 6 and the first glass substrate 3 becomes about 5 xcexcm.
Referring to FIG. 1F, the bonded first and second glass substrates 3 and 6 are taken out of the vacuum container xe2x80x98Cxe2x80x99 and an ultraviolet (UV) ray is directed to the seal 1, to set the seal 1, thereby finishing fabrication of the LCD.
However, the foregoing related art method for fabricating an LCD having the liquid crystal dropping method applied thereto has the following problems.
First, the sealant coating and liquid crystal dropping on the same substrate requires a long fabrication time period before the two substrates are bonded.
Second, as the sealant is coated and the liquid crystal is dropped on the first substrate while no progress is made for the second substrate, there is an unbalance of a fabrication process between the first and second substrates, which implies an ineffective operation of the production line.
Third, because the sealant is coated and the liquid crystal is dropped on the first substrate, the first substrate with a coat of the sealant applied thereto cannot be cleaned by an ultrasonic cleaner (USC). Therefore, as the sealant that is to bond the two substrates should not be washed away, particles cannot be removed, which may cause defective contact of the sealant during bonding.
Fourth, since a bonded state cannot be inspected while the bonded substrates are in the bonding container, alignment of the two substrates cannot be inspected, therefore a separate inspection apparatus is required.
Fifth, the alignment of the first and second substrates, with the liquid crystal or seal, which comes into contact with the second substrate, is likely to damage the alignment film on the second substrate that actually comes into contact with the liquid crystal or the seal, which deteriorates picture quality. Moreover, if the level of the first and/or second substrate is not correct, with a possibility of the first and second substrates coming into contact, the patterns on respective substrates are likely to be scratched and a thickness of the seal may not be even.
Sixth, the alignment of the substrates doubled, only varying a distance between the two substrates, has a limitation in accurate alignment of the two substrates.
Seventh, the bonding of the two substrates only by a physical force of the table and the second suction device may cause defective bonding due to non-uniform application of pressure throughout the substrate in the case where levels of the table and the second suction device are not correct.
Eighth, the introduction of air into the vacuum container for restoring the vacuum container to atmospheric pressure after the bonding may deteriorate a state of the vacuum container due to moisture contained in the air.
Accordingly, the present invention is directed to a method for fabricating a liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is to provide a method for fabricating an LCD having the liquid crystal dropping method applied thereto, which can shorten a fabrication time period, maximize efficiencies of alignment and pressure application, and check alignment of the substrates having a pressure applied thereto within a bonding chamber, for improving a productivity.
Additional features and advantages of the invention will be set forth in the description, which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the method for fabricating an LCD includes loading first and second substrates into a bonding chamber; aligning the first and second substrates; bonding the first and second substrates; venting the bonding chamber for applying a pressure to the bonded substrates; inspecting the substrates; and unloading the first and second substrates.
In another aspect of the present invention, there is provided a method for fabricating an LCD, including loading a first substrate having liquid crystal dropped thereon and a second substrate having sealant coated thereon; bonding the first and second substrates; venting the bonding chamber, for applying a pressure to the bonded substrates until a gap between the two substrates is below about 5 xcexcm, and unloading the first and second substrates.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.